The goal of this proposed research is to improve the efficacy of body weight supported treadmill training (BWSTT) in people post-stroke using a novel robotic therapy that applies forces to the paralyzed leg during the swing phase of gait. Impaired mobility is an important factor in determining the degree of physical disability after stroke. While up to 80% of individuals with stroke may ultimately recover the ability to walk short distance, most of them do not achieve the locomotor capacity necessary for community ambulation. As a result, there is a desire to develop new techniques to enhance the therapeutic effect in this population. While statistically significant improvements in walking recovery with BWSTT have been shown, it remains unclear whether therapeutic effects of such training are maximized. In addition, a major limitation of BWSTT is the requirement of greater involvement of physical therapist. Robotic assisted BWSTT demonstrates effectiveness in reducing therapist labor in locomotor training but shows relatively limited functional gains for some patients. Our goal is therefore to enhance the efficacy of BWSTT by applying assistance as needed or resistance as tolerated to the paralyzed leg during treadmill training. Evidence from animal studies indicates that gait retraining is more effective with assistance as needed than with a fixed trajectory paradigm. Similarly, results from human arm study indicated that causing adaptation by using error-augmentation training might be an effective way to promote functional motor recovery for patients with stroke. We postulate that providing assistance as needed or resistance as tolerated load based on the motor performance of the patient will improve the training outcomes of BWSTT through enhanced patient effort that effectively engages adaptive sensorimotor processes. Accordingly, our specific aims are: Aim1. Demonstrate motor adaptation to applied loads in individuals post stroke. Specifically, we aim to assess the motor adaptation to a resistance/assistance load in individuals post stroke. The muscle activities and kinematics of the lower extremities will be recorded to quantify the motor adaptive effects of resistance/assistance loads. We expect that leg muscle activity and limb kinematics will adapt to the applied loads and show aftereffects when removed;Aim 2. Improve gait training paradigms using resistance as tolerated strategy. We aim to assess locomotor recovery using resistance as tolerated/assistance as needed strategy to control the load applied to the paralyzed leg during BWSTT. Gait kinematics and clinical measurements of impairment and walking function will be obtained at pre, post training, and at the follow up. Significant improvements are expected in the BWSTT combined with resistance, compared to the assistance training group. The results from this study will lead to innovative clinical therapies aimed at improving locomotor recovery in patients post stroke. We anticipate that this technique will be useful for improving gait in individuals post stroke through robotic-assisted BWSTT. PUBLIC HEALTH RELEVANCE: The purpose of the proposed research is to improve the efficacy of body weight supported treadmill training (BWSTT) in people post-stroke using a novel robotic therapy that applies controlled forces to the paralyzed leg during walking. The results from this study will lead to innovative clinical therapies aimed at improving locomotor recovery in patients post stroke. We anticipate that this technique will be useful for improving gait in individuals post stroke through robotic-assisted BWSTT.